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Thread: Speculative Processing, To do or not to do?

  1. #1
    Join Date
    Mar 2001
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    Keats, KS USA
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    Got XLR8 MAChCarrier G3/500 for X-Mas (thanx to Santa and the Gurus!!!) with MACh Speed Control 2.6.1 to install into my 9500/200.

    My specs (via defaults) are:

    Processor Core:
    499.0MHz
    40 C (normal, is that to high???)

    Level 1 Cache:
    32K Data
    32K Instruction

    Backside Cache:
    1.0MB
    249.6MHz

    Motherboard Cache:
    512K-Disabled

    Motherboard Memory:
    288.0MB
    49.9MHz

    Things have been performing rock solid since I installed everything. I am happy with this performance right now, so I'm not doing any overclocking for a while.

    My question is whether or not I should use Speculative Processing. Since most of what I do is pretty routine (a lot of Pro Tools and SETi Data Units, plus a little bit of surfing), would I benefit from using it, or should I not worry about it.

    Thanks

    P.S.- How does one tell if you have a Carrier-MPe or regular Carrier??? The installer CD was boasting about MPe, but since I got a G3, I was wondering if I have a MPe or just regular Carrier.

    Kind of mute since I'll trade up to SSE (when I do)

    ------------------
    Bill

    "I made a conscience decision in a semi-conscious state"

  2. #2
    Join Date
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    My understanding on the issue is that the ONLY machines which should use peculative processing are the Mach V 86/9600s. Only the Mach V logic board supports Speculative Processing, and it can cause boot locks on other machines.

  3. #3
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    Bill,

    This is a question that has not been asked for quite awhile. My memory sucks but this what I recall. The only vintage Macs that are programmed for Speculative Processing are the 86/9600 Mach 5 Kansas motherboards, just those and no other 86/9600s that are not Kansas. Oh, and one PowerTower Pro motherboard modified by Trag with the Kansas ROMs, and another about to be modified by Trag, mine. One other way is with the Newer G3/G4 processor cards, supposedly allow Spec Processing. My S900 with Newer G3-500 I ran with Speculative Processing enabled with no problems. That card was rock solid in my S900. IMO, you should not enable it. Leaving it disabled also allows loading of Virtual Firmware and additional compatibility software.

    Carrier has 12 switches on the top of the card and CarrierMPe has 10 switches. k

  4. #4
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    Mar 2001
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    Thanks chrismenke & kaye!

    What about "Write-through" (in the Cache tab).

    There's not much explaination other than <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>"...is recommended for upgrades faster than 500MHz or any G4 or later upgrade in a pre-G3 machine."<HR></BLOCKQUOTE>.

    Even though I've lurked this forum for over a year now, I'm still a newbie at this Processor-Upgrade stuff.

    TIA!!!


    ------------------
    Bill

    "I made a conscience decision in a semi-conscious state"

    [This message has been edited by billbo (edited 04 January 2002).]

  5. #5
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    XLR8's newest versions of XLR8 Mach Speed Control patches the OldWorld ROMs to correct any Speculative Processing Problems. The only possible problems you would have is PCI ROMs and extensions that don't meet the necessary guidelines.

    I am using Speculative Processing on my PowerTower Pro (9500 Clone) without any problems using the following PCI cards: MilesU2W (Current OSX ROM flash), ATY Rage 128 (ROMs are okay), CompUSA USB/Firewire Combo card (No ROMs to conflict), IXMicro UltimateRes (Old card, but ROMs are okay), miroMOTION DC20 (No ROMs to conflict) and IXTV (No ROMs to conflict).

    The only sure test is to try it. If it doesn't result in random, unexplained crashes then you're good to go.

    About the Write-Through. Since your processor is running at 500MHz, It's a good idea to leave it on.

    [This message has been edited by lasvegas (edited 04 January 2002).]

  6. #6
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    Jun 2000
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    Hey billbo,

    Lasvegas is a demigod and has given you the safest answer, but I think you can get away with Write-Through disabled. There is a definite increase in Memory Throughput as demonstrated by Louie on these boards some moons ago. The only well-documented problem using Write-Back mode (Write-Through disabled) was in a PowerTower Pro with dual Miles2 cards. No joy unless Write-Through was enabled.

    LV: I didn't know that enabling SP was one of the newer fixes in the XLR8 Control software. Cool. Which version had this fix? I know the original fix was to disallow SP altogether.

    Regards x 2

    [This message has been edited by MacMikester (edited 04 January 2002).]

  7. #7
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    Version 2.5 first included a pdf file explaining the improvements and the function of Speculative Processing.

  8. #8
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    Hey lv,

    I'm still not sure I see a change in the MACh Control approach to this problem. Here is a quote from the ReadMe for the v. 2.6.1 download:
    Changing the status of Speculative Processing:
    The option to change the status of speculative processing is only available on systems where speculative processing may cause problems. If you have a choice, please note that enabling speculative processing is NOT recommended. Please refer to the XLR8 white paper.


    I've read the Newer and XLR8 white papers (some time ago now) about this issue. It still doesn't seem like XLR8 has developed a Virtual FirmwareȢ solution to allow speculative addressing of memory space while disallowing speculative addressing of hardware addresses (like the Newer hard-wired on-card solution did). Looks like SP still needs to be totally disabled for legacy macs without "G3-clean" ROMs. Is there something else in the XLR8 software that I am not aware of?

    Regards

  9. #9
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    Speculative addressing of hardware addresses is only done by software/firmware. XLR8's virtual firmware does correct this problem with the computer's ROMs, but cannot correct PCI card ROMs or poorly written Drivers. As I pointed out before, I've been using Speculative processing on my PowerTower Pro since version 2.5 without any problems.

  10. #10
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    So...

    If SP is turned off by Virtual FirmwareȢ, does this prevent "PCI card ROMs or poorly written drivers" from addressing memory and hardware addresses in a speculative manner?

    Conversely, if SP is turned on by Virtual FirmwareȢ, does it allow memory space speculation but prevent hardware address speculation by system firmware while allowing "PCI card ROMs or poorly written drivers" to speculate in both memory and hardware addresses?

    It seems both would need to be true for XLR8 to have fixed the problem as you say but still recommend not enabling SP in the most recent control software version.

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